The progress of modern technology has provided advancements in many technical areas. Image processing is definitely one of these areas. The use of compressed bit streams now enables large quantities of digital video data to be transmitted using relatively small bandwidths. Consistent with this progress in technology is the coming of HDTV. The introduction of HDTV will present many new technological issues. For example, studio environment processing of HDTV signals compressed in accordance with a known standard, such as motion picture expert group-type 2 (hereinafter, "MPEG-2") or the like, may require a new signal standard so that production editing and merging of HDTV signals is possible with minimal quality loss and degradation. Such production processing will generally require operating in the time (i.e., pixel) domain, as opposed to the frequency domain of coded images. Pixel domain processing requires decoding of an input HDTV MPEG-2 bit stream to the pixel domain. After processing is complete, the resulting images must be encoded back to an MPEG-2 bit stream for delivery as a studio output signal, or for storage and subsequent use in the studio environment.
One option for handling HDTV signals in the studio environment is to use high bit rates and restricted group of pictures (hereinafter, "GOP") structures. For example, one could consider using intra-coded (hereinafter, "I") macroblocks only, or a slightly more complicated GOP structure consisting of repeating I and bidirectionally predictive-coded (hereinafter, "B") pictures only (i.e., IBIBI). Closely spaced I frames can be used to simplify the processing for editing cuts and inserts. Some proposals suggest significantly increasing the MPEG-2 bit rate above the Grand Alliance's HDTV bit rate of 20 megabits per second to bit rates such as 129 and 225 megabits per second, which with the addition of overhead bits could conform to existing OC-3 and OC-12 telecommunications standards.
One major problem with the use of pixel processing is that MPEG-2 decoding and re-encoding will be necessary for a processing pass, and this will generally cause progressive signal quality degradation. One of the most significant causes of such degradation will be the non-linear processing, namely the dequantization and requantization, of the HDTV signal. Considering that as many as eight (8) of these studio processing passes may be required for a typical production run, the problem of HDTV signal degradation must be addressed and solved.